An experiment was conducted to measure thermal conductivity of a formulated food. The measurement was made by using a large plane plate of the food material, which was 5 mm thick. It was found, under steady-state conditions, that when a temperature difference of 35°C was maintained between the two surfaces of the plate, a heat-transfer rate per unit area of 4700 W/m 2 was measured near the center of either surface. Calculate the thermal conductivity of the product, and list two assumptions used in obtaining the result.

An experiment was conducted to measure thermal conductivity of a formulated food. The measurement was made by using a large plane plate of the food material, which was 5 mm thick. It was found, under steady-state conditions, that when a temperature difference of 35°C was maintained between the two surfaces of the plate, a heat-transfer rate per unit area of 4700 W/m 2 was measured near the center of either surface. Calculate the thermal conductivity of the product, and list two assumptions used in obtaining the result.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.10P: 1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss...

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2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss through a wall of 10-cm thickness is . If a thermocouple at the inner surface of the wall indicates a temperature of 22°C while another at the outer surface shows 6°C, calculate the thermal conductivity of the concrete and compare your result with the value in Appendix 2, Table 11.
1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4
3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
In an experiment to measure the thermal conductivity of a plate of unknown material with area 1 m2 and thickness 0.1m, one of its surfaces is maintained at 100 °C and the other at 20 °C and a heat at the rate of 100 kW was supplied across it. Determine the thermal conductivity of the hot plate. Is the material metallic, non-metallic, or gas/liquid?
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